NatWest says its smartphone app is being withdrawn for a routine update, but some customers have complained of fraudulent attacks on their accounts. Photograph: Pixellover RM 3/Alamy

NatWest has withdrawn a mobile phone app that allows consumers access to cash from ATMs without using a debit card. The move follows customer complaints about the theft of money from accounts.

The Get Cash app allows NatWest customers who have left their wallet at home to choose an amount between £10 and £100. NatWest then provides them with a secure cash code valid for three hours which can be used in any NatWest, RBS or Tesco cash machine to withdraw the chosen amount.

Other customers complained to Radio 4's Money Box programme after fraudsters withdrew hundreds of pounds from their accounts, each time being careful not to exceed the £100 limit.

A spokeswoman for NatWest denied the Get Cash feature of the app had been withdrawn because of the fraud cases, saying instead it was "temporarily unavailable to customers as a result of a planned update".

She added that it was being altered to lower the daily maximum withdrawal allowed. This is currently set at the limit associated with an individual customer's debit card, but is being "reduced to reflect the smaller withdrawals – typically between £30 and £50 made by NatWest customers".

NatWest does not expect to relaunch the Get Cash function before next week.